Sedan (nuclear test)

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Storax Sedan explosion

The Sedan Crater

Storax Sedan was a shallow underground nuclear test conducted in Area 10 of Yucca Flat at the Nevada Test Site on 6 July 1962 as part of Operation Plowshare, a program to investigate the use of nuclear weapons for mining, cratering, and other civilian purposes.^[1] The radioactive fallout from the test contaminated more US residents than any other nuclear test, and the Sedan Crater is the largest man-made crater in the United States, and is listed on the National Register of Historic Places.

[edit] Effects

Sedan was a thermonuclear device with a fission yield less than 30% and a fusion yield about 70%.^[2] The timing of the test put it within the Operation Storax fiscal year, but Sedan was functionally part of Operation Plowshare, and the test protocol was sponsored and conducted by Lawrence Livermore National Laboratory with minimal involvement by the United States Department of Defense. The explosive device was lowered into a shaft drilled into the desert alluvium 194 m (640 ft) deep.^[2] The fusion-fission blast had a yield equivalent to 104 kilotons of TNT (435 terajoules) and lifted a dome of earth 290 feet above the desert floor before it vented at three seconds after detonation, exploding upward and outward displacing more than 11,000,000 t (11,000,000 LT; 12,000,000 ST) of soil.^[3] The resulting crater is 100 m (330 ft) deep with a diameter of about 390 m (1,300 ft). A circular area of the desert floor five miles across was obscured by fast-expanding dust clouds moving out horizontally from the base surge, akin to pyroclastic surge.^[4] The blast caused seismic waves equivalent to an earthquake of 4.75 on the Richter scale.^[1] The radiation level on the crater lip at 1 hour after burst was 500 R per hour.

[edit] Fallout

US counties that measured the highest levels of radioactive fallout from both Sedan and "Small Boy" of Operation Sunbeam, detonated eight days later

The ten highest radiation exposures to residents from US continental nuclear testing

The Sedan shot resulted in a radioactive cloud that separated into two plumes, rising to 3 km (10,000 ft.) and 4.9 km (16,000 ft.) The two plumes headed northeast and then east in roughly parallel paths towards the Atlantic Ocean.^[5] A large amount of nuclear fallout was dropped along the way, narrowly dispersed in a relatively small number of United States counties. Detected radioactivity was especially high in eight counties in Iowa and one county each in Nebraska, South Dakota and Illinois. Most heavily affected counties were Howard, Mitchell and Worth counties in Iowa, as well as Washabaugh County in South Dakota, an area that has since been incorporated into Jackson County and is wholly within Pine Ridge Indian Reservation. These four counties measured maximum levels higher than 6,000 microCuries per square meter.^[6]

Of all the nuclear tests conducted in the USA, Sedan ranked highest in overall activity of radionuclides in fallout. 880,000 Curies of radioactive Iodine-131, an agent of thyroid disease, was released into the atmosphere.^[7] Sedan ranked first in percentages of these particular radionuclides detected in fallout: ¹⁹⁸Au, ¹⁹⁹Au, ⁷Be, ⁹⁹Mo, ¹⁴⁷Nd, ²⁰³Pb, ¹⁸¹W, ¹⁸⁵W and ¹⁸⁸W. Sedan ranked second in these radionuclides in fallout: ⁵⁷Co, ⁶⁰Co and ⁵⁴Mn. Sedan ranked third in the detected amount of ²⁴Na in fallout. In countrywide deposition of radionuclides, Sedan was highest in the amount of ⁷Be, ⁵⁴Mn, ¹⁰⁶Ru and ²⁴²Cm, and second highest in the amount of deposited ^127mTe.^[6]

Sedan's fallout contamination exposed a little under 7% of Americans to radiation, more than 13 million people; the highest number exposed by any nuclear test explosion in the continental USA. Sedan's effects were similar to shot "George" of Operation Tumbler-Snapper, detonated on June 1, 1952, which also exposed about 7% of American citizens to radioactive fallout, though in 1952 the country's population count was lower than in 1962; shot George exposed about 11 million people to radioactive fallout. Uncertainty regarding exact amounts of exposure prevent knowing which of the two nuclear tests exposed the greatest percentage of the American populace; George is listed as being the highest exposure and Sedan second highest by the United States Department of Health and Human Services, Centers for Disease Control and Prevention, and the National Cancer Institute.^[8][9]

[edit] Conclusions

The Plowshare project developed the Sedan test in order to determine the feasibility of using nuclear detonations to quickly and economically excavate large amounts of dirt and rock. Proposed applications included the creation of harbors, canals, open pit mines, railroad and highway cuts through mountainous terrain and the construction of dams. Assessment of the full effects of the Sedan shot showed that the radioactive fallout from such uses would be extensive. Public concerns about the health effects and a lack of Congressional support eventually led to the abandonment of the concept.^[10] No such nuclear excavation has since been undertaken by the US,^[11] though the Soviet Union continued to pursue the concept through their program Nuclear Explosions for the National Economy.

[edit] Misunderstanding in 2005

On March 2, 2005 Ellen Tauscher, a Democratic member of the U.S. House of Representatives representing the state of California, gave congressional testimony on the containment of nuclear testing debris, using the Sedan test as an example of one which produced a considerable amount of radioactive fallout. The word Sedan was incorrectly transcribed as Sudan in the Congressional Record. Within days of the error, the international community took notice. Sudanese officials responded to this stating that "the Sudanese government takes this issue seriously and with extreme importance," and China's Xinhua General News Service even went so far as to publish an article claiming that the Sudanese government had blamed the U.S. for raising cancer rates among the Sudanese people.^[12] Despite the U.S. embassy in Khartoum issuing a statement regarding the error, the Sudanese Foreign Minister, Mustafa Osman Ismail, stated that they would continue investigating.^[13]

[edit] See also

• Chagan (nuclear test)
• Peaceful nuclear explosions

[edit] References

[edit] External links

• US government movie about the Sedan test
• of the Sedan Underground Nuclear Test video
• Virtual-Reality tour of Sedan Site

Coordinates: 37°10′37″N 116°2′46″W / 37.17694°N 116.04611°W / 37.17694; -116.04611